


That Night Under the Stars

by The_Exile



Category: Undertale (Video Game)
Genre: Angst and Hurt/Comfort, Biting, Claws, Dimension Travel, Headcanon, Implied/Referenced Character Death, M/M, Rough Kissing, Sensation Play, Spoilers, physical damage from glitching and paradox, unwise scientific experimentation
Language: English
Status: Completed
Published: 2018-06-05
Updated: 2018-06-05
Packaged: 2019-05-18 17:07:56
Rating: Mature
Warnings: Major Character Death
Chapters: 1
Words: 1,355
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14856764
Author URL: https://archiveofourown.org/users/The_Exile/pseuds/The_Exile
Summary: Gaster is away for longer periods of time on increasingly dangerous expeditions. He's looking increasingly ill and Asgore worries about him, sometimes even about the wisdom of the experiments in the first place, so he helps his loyal subject to remember his duty to come home. Gaster made a promise, though, and he can't break it even for the person he made the promise to, not when Asgore is getting worse himself and is even more stubborn about admitting it.Also featuring Sans and Alphys as young apprentices.





	That Night Under the Stars

**Author's Note:**

  * For [ShamanicShaymin](https://archiveofourown.org/users/ShamanicShaymin/gifts).



He wished he had cheeks to flush red, a heart to thump louder in the echoing cavity of his skull. It would have made sense of the way he felt right now, hot and breathless despite the trouble he was having interacting with his native world properly after spending so long in the void of Offscreen or the secret Unused sectors of the cosmos. He couldn't stop tripping up because his feet were clipping through the floor, generating angrily sparking static, yet he couldn't tear his gaze away from the man who had summoned him to a private audience.

The Mountain King Himself was caressing his skeletal, melted, lopsided grinning mask of a face with those broad, strong, lush white-furred hands of his. A sad frown, a look of gentle concern, crossed his horned, hircine face, those burning bronze eyes of his flaring up as he looked into Gaster's own hollow, dark eye sockets, humming almost mechanically with life of a different sort but life nonetheless. His claws were unsheathed, scraping ever so lightly down Gaster's hard to pierce carapace, just managing to etch a furrow that couldn't immediately be rubbed away.

Gaster was not logically supposed to be able to feel it but he did. Not as a purely physical sensation but as something that sparked between them, a signal through a connection between them that was deeper and both simpler and infinitely more complicated than words, a level of the Soul beyond what his research could fathom - also something other than the static discharge that had made His Highness look even more indignantly fluffy than usual. Asgore had attempted to smooth the errant fur down several times but to no avail. Gaster tried to help but just made it worse. Now the King under the Mountain was leaking white pixels from the fur that was wildly standing on end, all down his hands and arms. 

"You know that you needn't look your magnificent best to impress me," Gaster smiled, aware that he was at a stage of their relationship where he could get away with some light teasing (his wife had apparently called him 'Fluffybuns' behind closed doors, for Angel's sake...), "I'm not in a line of work where I can spread rumours even if I wanted to do such a thing, and I... am not exactly one to talk, either."

"That has not happened before, Gaster. You can joke through the pain but you cannot hide from me that you are in some kind of trouble. There are more cracks in that mask of yours, too, more warping around the affected spot. More of that sparkling white residue, too. What is that white stuff, Gaster?" he demanded, "Does it come from the worlds you walk through? The space between the worlds? Or is it your Soul leaking out now that your shell is failing?"

He shook his head, several different white pinpricks of light in his eye sockets winking on and off in rapid succession, "It's not as bad as it looks."

"It isn't? You've been gone out there for a while. You're supposed to take regular breaks. We aren't native to the void and we're not meant to survive in it. I don't understand whatever it is you do out there but I can see you're deteriorating, Gaster. I am ordering you to get repairs done. Now."

"Self-repair is difficult..."

"Then have your brother and apprentice do it, the talented ones you always give me such glowing reviews of."

"Truth be told, I don't think Alphys quite has the talent for extradimensional travel. Other things, maybe, but she doesn't have the open-mindedness or the mental endurance. Sans isn't quite at the stage of being fully involved in the project yet. I'm trying to teach him to recognise his limits, not to blindly follow me into places..."

"Places that you can't actually handle yourself yet?" Asgore raised one alarmingly fluffy eyebrow.

"It's not the danger of this particular location, it's how far out I have to travel, how long I have to be away from home base to reach anywhere new... how weird it's all getting, so far away from the conceptual norm for us monsters. It starts to change who you are at a fundamental level, not just how you think."

"I like you the way you are, Gaster, and I will not lose you, not even to this project."

"But I promised you..." he growled as another sudden flux of soul-energies snarled within his skull-mask, sending an arc of white lightning whipping across the melted side of his face, "If... when I succeed... I'll find a place we can live, an exit that's not guarded by people who will probably just lock us up again. A peaceful place. It might not be stable now but I'll build the path once I find the route. And... more importantly... Your Highness, the Void is a place where literally anything can happen, any variation on the laws of what is possible could be made available. That... that side project of ours..."

"Frankly, I am having my doubts over the wisdom of ever restarting that 'side project' again. There are lines we cannot cross, doors we cannot open, and is not... that place... the one true sanctuary of the soul?" 

"But, my King, that day still hurts you, I can see your pain in your eyes, hear it in your voice..."

"And yours is even more obviously etched on your face."

"I can handle a little wear and tear from glitches and paradoxes. It's what I built myself for. Compared to your pain, it is nothing..."

"And your apprentice who looks up to you... your brothers... your own two brothers... how will they feel if they should lose you?" the King's eyes flared up and seared into his, sharper than the points of his trident, "How do you think I would feel? You are aware of what you mean to me, yes?"

"Your Highness, I... it would be importunate of me to..."

"I don't think you really do," Asgore finished for him, "So let me give you a reminder. Something a little more permanent, so you can carry it with you no matter where you take it into your head to go."

 

That was when Asgore, with that famed lightning speed and grace belying his broad frame, leaned forward, swept Gaster into his powerful arms and the dark folds of his cloak and kissed him - firmly, with fangs drawn, like the beast he resembled. It burned him, paralysed his senses, sent surges of raw energy deep into his soul. That mark glowed where he had been bitten, remained even when he almost lost that arm in the next glitch-storm he was trapped in. 

That was when he took his first real break in months, let Sans patch him up, endured his endless questions, politely explained which actions of Gaster's would get Sans immediately fired from his position if he ever tried to emulate. He even put up with Alphys' nagging in return. The lizard had been working on sophisticated robots that would house souls to make them a little more durable - an admirably practical solution, if only in the short term, as even robots broke down and the mountain only had so many natural resources. At least Alphys was actually addressing the short term situation at all, not just chasing dreams and avoiding the real world. At least Alphys was doing something not entirely likely to get her annihilated from existence... 

Still, he had made a promise. And until he ever saw the King smile, even once, or at the very least leave his throne room again, he would keep to his word and do the duty that only a creature like Gaster, something that now registered as fifty per cent unused according to his own scanners, with so much of himself already scattered around so many other planes, ever could. 

But now a part of his soul would always still be in that throne room, back in that warm, comforting darkness, on that one night under the throne room’s perfectly still crystalline stars.


End file.
